Gen I rear rotor thickness

[Harald]

We all know that the Gen II weighs more than a Gen I FJR, but it looks like Yamaha tried to keep the weight down by going to thinner rear rotors. According to my manual and actual measurements, my 07 has a new rear rotor thickness of 5mm with a wear limit of 4.5mm. Iggy's comparison matrix shows that rear rotors are interchangeable amoung all years. Because my rear rotor is measuring 4.65mm, I checked fleabay to see what used rotors are going for. The ones I'm seeing are listed as coming off Gen I FJR's and the thickness are listed at 6mm and 5.92mm for the 2 that I have dimensions for.

So I'm wondering if Gen I rear rotors are really thicker (anyone actually mic theirs)? Can someone with a Gen I manual please check the specs? As long as the bolt pattern and diameter is the same, I don't see why a thicker rotor wouldn't work because I can't imagine you couldn't push a caliper piston another 1mm into it's bore to fit on a thicker rotor.

Assuming the Gen I rotor is thicker and would work on a Gen II, it would be good to know at replacement time. The only downside would be that it would give all you Gen II haters another reason to bash us for having wimpy rotors.

 

[Bustanut joker]

Mine is just under 6 mm. Not sure of the mileage as the dash is on the shelf but 15k is about right.

 

[ionbeam]

These are the actual measurements from my Gen I, as posted in another thread where not2shabby was looking to replace his rotors.

I just took my micrometer to the rotors and they average 4.55mm at all the un-swept areas. At 72k miles, having used various brake pads over those miles, with some trepidation I measured the swept areas of my rotors and discovered that they are worn all the way down to 4.50mm.

...I just checked (the rear rotor) too. Spec is 5mm, I measured 5.0mm.

From the Gen II FSM: Front rotor spec is 4.5mm and rear rotor spec is 5mm. Service limits are 4.0mm and 4.5mm.

 

[Harald]

These are the actual measurements from my Gen I, as posted in another thread where not2shabby was looking to replace his rotors.

I just took my micrometer to the rotors and they average 4.55mm at all the un-swept areas. At 72k miles, having used various brake pads over those miles, with some trepidation I measured the swept areas of my rotors and discovered that they are worn all the way down to 4.50mm.

...I just checked (the rear rotor) too. Spec is 5mm, I measured 5.0mm.

From the Gen II FSM: Front rotor spec is 4.5mm and rear rotor spec is 5mm. Service limits are 4.0mm and 4.5mm.

Your measurements have me confused even more. :crazy: I would assume that the unswept area would be factory thickness, but your 4.55mm is less than Gen II factory thickness? Or are your measurements for FRONT rotors?

Bust says his mic out just less than 6mm. And here's the one FLEABAY Auction where they show the mic at 5.92mm. I know that the unswept surface (along the outside edge) of my rear rotor measures 5mm.

 

[ionbeam]

Gen I front rotors: 4.55mm at the un-swept areas, the swept areas of my front rotors are 4.50mm

Gen I rear rotors: The un-swept area of the rear rotors are 5.2mm and the swept area of the rear rotors are 5.0mm.

It appears that the rotors are just a smidgen more than specification. I used both a micrometer and digital vernier calipers.

I would cordially invite Bust to try his check again, if it still reads a bit less than 6mm he needs to have his gauge calibrated Or, he needs a nip or two to steady his hands when making the measurement.

...Bust says his mic out just less than 6mm. And here's the one FLEABAY Auction where they show the mic at 5.92mm...

Cheap Harbor Freight calipers?